Any digital transmission system may be disturbed by a large number of causes, such as the imperfection of the transmission medium (for example, a radio relay link), the presence of noise on the transmission channel, radio interference or a breakdown. These disturbances are manifested, on the side of the user, by an error rate in the bit stream used and by periods of time during which transmission is interrupted, which poses a general technical problem. When the cost of the bit stream is not too high, more specifically in ground-based communication networks, a simple prior-art solution for solving the general technical problem mentioned above consists of diversity transmission duplicating the signal to be transmitted, transmitting the signal over two separate channels and selecting the better of the two signals on reception. The present invention in this context is related to the doubling of the digital channel, in which situation the particular problem is posed of correcting the phase of the two received signals. Among other applications, this phase correction allows the receiving arrangement to switch over from one signal to another without causing errors as a result of the loss of the frame clock, and so on. In these conditions it becomes possible to change from a signal of frame TRA to a signal of frame TRB as often as necessary, in response to the respective errors in each frame, using the maximum errorless period of time of each digital path without the risk of degrading the composite signal.
In order to re-establish signal equalization on two digital paths that carry the same information it is known, more specifically from U.S. Pat. No. 4,218,654, to form a negative feedback loop between the output and control input of a variable delay circuit inserted in a first information channel, while a control circuit which also receives the same information present on a second channel is incorporated in the loop. Such an arrangement leads to drawbacks inherent with any control element, which are the complexity of its use and its slowness.